Sure? But I'm not talking about what's easier, I'm talking about what is. Go and watch any ep where you see the uniform clearly, there is no material break at the waist. They are cinched with (elastic?) at the sides, but the material and zip continues on down past the point where the "jacket" ends when taken off.^ You don't think it would have been easier to simply make it a two-piece from the get-go, just so the actors would have an easier time getting into and out of uniform?
First pic I could find showing clear lack of jacket/pants split...
http://ds9.trekcore.com/gallery/albums/1x01/emissary227.jpg
Tom going into brig...
http://voy.trekcore.com/gallery/albums/5x09/thirtydays_019.jpg
Tom in brig...
http://voy.trekcore.com/gallery/albums/5x09/thirtydays_053.jpg
His "jacket" comes off and the undershirt is discarded for a smaller one.